1. Field of the Invention
The present invention relates to a nailing machine, and particularly to a nailing machine having an idle driving prevention device.
2. Description of the Prior Art
Japanese Utility Model Publication No. 2-28007 discloses a nailing machine having an idle driving prevention device which serves to prevent damage to a damper of the nailing machine or to prevent damage to a work. The nailing machine of this publication includes a driver guide and a contact arm which is vertically movably mounted on the driver guide. The contact arm is interlocked with a trigger in such a manner that the operation of the trigger is not effectuated unless the contact arm is moved to an upper position through abutment on the work. The idle driving prevention device is provided between the contact arm and a pusher of a magazine. The pusher is operable to feed nails stored within the magazine one after another into a nail guide channel formed in the driver guide. When no nails exist in the magazine or when only a few nails remain within the magazine, the idle driving prevention device mechanically stops the vertical movement of the contact arm, so that the trigger cannot be operated to drive the nails.
However, with this conventional nailing machine, the idle driving prevention device cannot function effectively when an operator performs an operation called "dragging nail driving operation" or "continuous nail driving operation" where the operator repeatedly pulls the trigger with the contact arm held in abutment on the work. Thus, since the contact arm is held in the upper position, the operation of the trigger is kept effective even if the nails within the magazine have been driven out.
A similar problem may be caused with a nailing machine which has been proposed recently and which has a lock mechanism for fixing a contact arm in its upper position for the convenience of "dragging nail driving operation".